cxa_demangle: fix -Wimplicit-fallthrough for GCC:7

Use the C++11 (formalised in C++17) tag to indicate a fallthrough in the
switch case.  Silences a -Wimplicit-fallthrough warning with gcc:7

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@305173 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cxa_demangle.cpp b/src/cxa_demangle.cpp
index 3707dca..a2c384e 100644
--- a/src/cxa_demangle.cpp
+++ b/src/cxa_demangle.cpp
@@ -2258,7 +2258,7 @@ parse_type(const char* first, const char* last, C& db)
                                 break;
                             }
                         }
-                        // drop through
+                        [[gnu::fallthrough]];
                     default:
                         // must check for builtin-types before class-enum-types to avoid
                         // ambiguities with operator-names